CMOS RLC and crystal oscillators based on current conveyors

Analysis and design of RLC and crystal oscillators based on current conveyors, in 1.5 μm CMOS integrated technology, are described. Maximal operating frequencies are 350 and 50 MHz, respectively     

The relationship between localised SAR in the arm and wrist current

Calculations are presented of the specific energy absorption rate, SAR, in the lower arm of the NRPB anatomically realistic voxel model. NORMAN, for induced currents from 100 kHz to 80 MHz. The wrist region has a narrow cross section and contains little high conductivity muscle, comprising mainly low conductivity bone, tendon and fat. Consequently there is a channelling of the current through the high conductivity muscle, which produces high, localised values of the SAR. Values averaged over 10 g and 100 g of tissue are calculated as a function of the current flowing through the wrist.     

Vacuum field-emission triode based on electron multiplier concentrator

The design and technology of manufacturing a vacuum field-emission triode (VFT) based on an electron multiplier concentrator that plays the role of a field-emission cathode capable of ensuring a significantly greater current density as compared to that provided by the other existing electron emitters. Experimental current-voltage characteristics of the VFT are presented. The possibility of creating integrated circuits based on the proposed device is discussed.     

Increasing the negative charge of a macroanion in the gas phase via sequential charge inversion reactions

Protonated and deprotonated biological molecules in the gas phase play an important role in life sciences research. The structural information accessible from the ions is highly dependent upon their charge states. Therefore, it is desirable to develop means for increasing absolute charge states, particularly for ionization methods, such as MALDI, that yield relatively low charge ions. The work presented here demonstrates the formation of a doubly deprotonated polypeptide or oligonucleotide ion (dianion) from a singly deprotonated analogue via two sequential ion/ion proton-transfer reactions involving charge inversion. The high exoergicity and the large cross section arising from the long-range attractive Coulomb potential of ion/ion reactions make this process plausible. In this example, an overall efficiency of conversion of singly charged ions to doubly charged ions of roughly 8% for polypeptide was noted while lower efficiency (roughly 2%) observed with an oligonucleotide is likely due to a greater degree of neutralization. No other approach to increasing the net negative charge of an anion in the gas phase has as yet been reported.     

Phosphopeptide anion characterization via sequential charge inversion and electron-transfer dissociation

Sequential ion/ion reactions have been used to characterize phosphopeptides present in relatively simple peptide mixtures, including one generated from the tryptic digestion of alpha-casein. The phosphopeptides in these mixtures gave rise to either low or no signals via positive ion electrospray ionization. Strong signals, however, were generated in the negative ion mode. An initial ion/ion reaction that employed multiply protonated amino-terminated dendrimers converted phosphopeptide anions to the doubly protonated species. The doubly charged cations were then subjected to ion/ion electron transfer to induce dissociation. Electron-transfer dissociation of doubly positively charged phosphopeptides yields characteristic c- and z-type fragment ions by dissociation of the N-C(alpha) bond along the peptide backbone while preserving the labile posttranslational modifications. These results illustrate the ability to alter ion charge after ion formation and prior to structural interrogation. Phosphopeptides provide an example where it can be difficult to form strong doubly charged cation signals directly when they are present in mixtures, which, as a result, precludes the use of electron-transfer dissociation as a structural probe. The sequential ion/ion reaction process described here, therefore, can provide a new capability for structural interrogation in phosphoproteomics.     

Multi-input differential current conveyor, CMOS realisation and application

The adjoint circuit of a multiple output second-generation current conveyor (MOCCII) is investigated. It is found that the adjoint circuit of MOCCII is an multi-input differential current conveyor (MIDCC). A CMOS realisation of the MIDCC with three plus-type input terminals and two minus-type input terminals is described. As an example of applying the MIDCC, the transforming of a current-mode filter using MOCCIIs to its adjoint voltage-mode filter using MIDCCs is discussed.     

Proposal for electro-optic multiplier based on dual transverse electro-optic Kerr effect

A novel electro-optic multiplier is proposed, which can perform voltage multiplication operation by use of the Kerr medium exhibiting dual transverse electro-optic Kerr effect. In this kind of Kerr medium, electro-optic phase retardation is proportional to the square of its applied electric field, and orientations of the field-induced birefringent axes are only related to the direction of the field. Based on this effect, we can design an electro-optic multiplier by selecting the crystals of 6/mmm, 432, and m3m classes and isotropic Kerr media such as glass. Simple calculation demonstrates that a kind of glass-ceramic material with a large Kerr constant can be used for the design of the proposed electro-optic multiplier.     

The relationship between charge passed and the chloride concentrations in anode and cathode cells using the accelerated chloride migration test

In this study the electrochemical technique is applied to accelerate chloride ion migration in cement-based material to estimate its permeability. Specimens with six fine aggregate volume fractions were cast and tested. For all test series, the chloride concentrations both in anode and cathode cells as well as the electrical current were simultaneously monitored in the accelerated chloride migration test. The chloride migration rates of anode and chloride cells were used to assess the permeability of cement-based materials. A good correlation was observed between the chloride migration rate of anode cell and cathode cell. And, a good correlation was also observed between the chloride concentration in anode cell, the chloride concentration in cathode cell and charge passed obtained from the accelerated chloride migration test.

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Résumé La technique electrochimique est appliquée pour accélérer la migration des ions chlorure dans des matériaux à base de ciment pour estimer leur perméabilité. Des échantillons avec six granulats fins ont été préparés et testés. Dans tous ces tests, les concentrations dans les cellules anode et cathode ainsi que les courants, électriques ont été simultanément suivis. Le taux de migration dans les cellules anode et cathode a été utilisé pour évaleur la perméabilité des matériaux testés. Une bonne corrélation a été observée entre le taux de migration de chlorure dans la cellule anode et dans la cellule cathode. Une bonne corrélation a aussi été observée entre ces concentrations et la charge passée obtenue de ces tests de migration de chlorure accélérés.

     

A relationship between diffusion and charge transfer parameters in a binary melt formed during contact melting

Theoretical and experimental data on the mass and charge transfer, charge transfer during contact melting, and hydrodynamic mixing of inert labels introduced into a contact between two dissimilar metals are analyzed and an integral criterion for the charge and mass transfer direction in this system is formulated. According to this criterion, which is valid in all the known binary systems of this type, (Ω₁–Ω₂)(D ₁–D ₂)]=−z ₁*–z ₂*, where Ω_i, D _i , and z _i * are the atomic volumes, partial diffusion coefficients, and effective charges of light (i=1) and heavy (i=2) components.     

Comparison between techniques based on charge characterisation and capillary suction time for assessing the dispersion characteristics of concentrated slurry

Achieving a stable dispersion with high solid loading is pre-requisite in many conventional/emerging ceramic forming processes. Hence, assessing the quality of dispersion is one of the critical aspects to be considered during forming process to ensure the final product quality. There are several direct/indirect techniques to assess the quality of dispersion. Many are optical methods, which generally require dilution of the suspension, with consequent alteration of the equilibria. This complicates the system unless particular care is taken to compensate for the dilution process. Many times it has been observed that a dispersant, that provides good dispersion at low solids concentration will not necessarily provide good dispersion at high solids concentration.This paper compares two indirect techniques, namely, particle charge detector (PCD) using the principle of Streaming Potential and capillary suction time (CST) apparatus based on the principle of capillary suction pressure to study the effectiveness of a dispersant for maximum dispersibility.     

匹配场反演阵形估计算法的试验研究

传统的阵形估计算法都基于这样一个假设,即声传播为平面波或球面波模型,在浅海应用条件下,多途效应显著,该假设失效,造成此类算法的性能下降。提出了一种基于匹配场反演的阵形估计算法,采用简正波模型对声场建模,将多途建模为不同号数的简正波,从而消除了多途效应的影响;并且通过合理地选择目标函数,使算法对环境参数的扰动具有一定的宽容性;利用柔性阵的线性约束,将阵形畸变用弧线建模,使问题简化,在缺少声源精确位置等先验知识的前提下,仍能实现阵形的准确估计。理论仿真和试验结果表明,该算法是有效的。     

A unified drain current model for nanoscale double-gate and surrounding-gate MOSFETs incorporating velocity saturation

A unified drain current model for undoped or lightly doped symmetric double-gate and surrounding-gate MOSFETs incorporating velocity saturation effect is proposed in this paper. The unified charge-based core model for undoped or lightly doped double-gate and surrounding-gate MOSFETs is presented first based on the previously published separate models. Caughey-Thomas engineering mobility model with its exponent factor n = 2 is then integrated self-consistently into the unified drain current model development of the two device structures. Extensive two dimensional and three dimensional device simulations are performed to validate the proposed model. Good agreements of the output and transfer characteristics between the unified model and the numerical simulations are obtained for both the double-gate and surrounding-gate MOSFETs. Symmetry property of the proposed unified current model is obtained with the exponent factor n = 2 in Cauhey-Thomas Model.     

Full-field phase error compensation method based on relationship between unwrapped phase and phase error

The three-dimensional reconstruction in phase-measuring profilometry (PMP) usually involves the phase error caused by the gamma effect of the projector. In this study, the relationship between the unwrapped phase and the phase error of every pixel is analysed, and an effective full-field phase error compensation method based on this relationship is proposed for the reduction of every pixel error. In our optimized PMP system, the full-field phase error can be detected by directly fitting the unwrapped phase of the reference plane. In addition, the relationship between the unwrapped phase and the phase error can be established by creating a phase-error lookup table for the phase error compensation of every pixel. The experimental results demonstrate the effectiveness of the proposed method in practical PMP, and the measurement errors can be reduced by a factor of least 10.     

The current column contraction and ion charge increase induced by the current build-up in a pulsed vacuum discharge

It is shown that three current build-up regimes may be realized in a pulsed vacuum discharge, depending on the relationship between the pulse duration τ and the characteristic times of the plasma flow (τ_L) and the cathode spot spreading (τ_S). For a rapid build-up (τ<τ_L), the cathode plasma jet exhibits the neck formation with high values of the plasma temperature and density. At a slow current increase (τ_L<τ<τ_S), the current column is subject to a uniform magnetic contraction, while at a very slow current growth rate (τ>τ_S), the contraction becomes insignificant. The first two cases give rise to additional nonequilibrium ionization in the current column, which leads to the ion charge increasing with the current. The third case is characterized by a “frozen” ion composition corresponding to the plasma parameters in the near-cathode region.     

基于CMOS图像传感器的微小变形测量系统

近年来，图像处理在微小变形的测量中应用越来越广泛，它具有方便灵活、对被测对象没有任何伤害等优点，且只需对被测对象进行拍照，然后对图像进行处理分析，利用亚像素法原理即可精密测量出试样的微小变形。因此，利用AT89C51与CMOS图像传感器OV5017组成DMA方式数据采集系统，FT245BM虚拟USB口与PC机通讯，实现了对纵向和横向两个方向微小变形的无接触精密测量，且精度高成本低。     

Reagent anions for charge inversion of polypeptide/protein cations in the gas phase

Various reagent anions capable of converting polypeptide cations to anions via ion/ion reactions have been investigated. The major charge inversion reaction channels include multiple proton transfer and adduct formation. Dianions composed of sulfonate groups as the negative charge carriers show essentially exclusive adduct formation in converting protonated peptides and proteins to anions. Dianions composed of carboxylate groups, on the other hand, show far more charge inversion via multiple proton transfer, with the degree of adduct formation dependent upon both the size of the polypeptide and the spacings between carboxylate groups in the dianion. More highly charged carboxylate-containing anions, such as those derived from carboxylate-terminated polyamidoamine half-generation dendrimers show charge inversion to give anion charges as high in magnitude as -4, with the degree of adduct formation being inversely related to dendrimer generation. All observations can be interpreted on the basis of charge inversion taking place via a long-lived chemical complex. The lifetime of this complex is related to the strengths and numbers of the interactions of the reactants in the complex. Calculations with model systems are fully consistent with sulfonate groups giving rise to more stable complexes. The kinetic stability of the complex can also be affected by the presence of electrostatic repulsion if it is multiply charged. In general, this situation destabilizes the complex and reduces the likelihood for observation of adducts. The findings highlight the characteristics of multiply charged anions that play roles in determining the nature of charge inversion products associated with protonated peptides and proteins.     

Characterization of charge collection in CdTe and CZT using the transient current technique

The charge collection properties of Cadmium–Telluride (CdTe) and Cadmium–Zinc–Telluride (CZT) in comparison with Silicon (Si) are presented using the transient-current technique (TCT) where the current pulses are generated by -particles emitted from an ²⁴¹Am source. From the recorded current pulse shapes, the charge collection efficiency, the charge carrier mobility and the electric field distribution inside the detectors are extracted. In particular, the signals of the compound semiconductors CdTe and CZT are interpreted with respect to the build-up of space–charges in the sensor volume and the subsequent deformation of the electric field. As high-quality CdTe and CZT samples are now commercially available, the knowledge of these material characteristics is of outmost importance for the application of CdTe and CZT in X-ray imaging.

In addition, the paper describes the influence of Ohmic and Schottky contacts on the current pulses in CdTe as well as the effects of polarization, i.e. the time-dependent degradation of the detector signals due to the accumulation of fixed charges within the sensor.     

Julia集和Mandelbrot集的反演变换

论文讨论了居里叶集与曼德尔布罗特集的反演变换问题,通过扩充复平面上关于任意定点的反演变换,获得了两类共轭函数。使得这两类共轭函数的居里叶集与曼德尔布罗特集,恰好是原居里叶集与曼德尔布罗特集关于定点的反演变换,并运用逃逸时间算法绘制居里叶集和曼德尔布罗特集的反演图。     

基于MSET和SPRT的内燃机气阀机构振动监测

提出了一种基于多元状态估计(Multivariate State Estimation Techniques,MSET)和序贯概率比检验(Sequential Probability Ratio Test,SPRT)的内燃机气阀机构振动监测方法.在该方法中,首先建立正常工况下各监测参数之间的关联模型;然后根据系统当前观测特征向量与各建模样本特征向量之间的相似性程度,使用MSET对当前观测特征向量进行估计,得到与观测特征向量相对应的估计残差;最后使用SPRT对观测特征向量的估计残差进行均值和方差检验,确定系统的工作状态.试验中,通过设置不同的气阀间隙大小来模拟内燃机气阀机构不同程度的异常工况,以整周期缸盖振动信号幅值域特征作为系统工况监测参数.试验结果表明,MSET可有效增强故障状态下的信号特征呈现,而SPRT可在较少的周期内实现内燃机气阀机构异常工况的识别,MSET和SPRT的结合有效地实现了对内燃机气阀机构异常工况的早期监测.